1. Field of the Invention
The present invention pertains to wireless telecommunications, and particularly to acquisition of status information by a control node of a radio access network.
2. Related Art and Other Considerations
In a typical cellular radio system, mobile user equipment units (UEs) communicate via a radio access network (RAN) to one or more core networks. The user equipment units (UEs) can be mobile stations such as mobile telephones (“cellular” telephones) and laptops with mobile termination, and thus can be, for example, portable, pocket, hand-held, computer-included, or car-mounted mobile devices which communicate voice and/or data with radio access network.
The radio access network (RAN) covers a geographical area which is divided into cell areas, with each cell area being served by a base station. A cell is a geographical area where radio coverage is provided by the radio base station equipment at a base station site. Each cell is identified by a unique identity, which is broadcast in the cell. The base stations communicate over the air interface (e.g., radio frequencies) with the user equipment units (UE) within range of the base stations. In the radio access network, several base stations are typically connected (e.g., by landlines or microwave) to a radio network controller (RNC). The radio network controller, also sometimes termed a base station controller (BSC), supervises and coordinates various activities of the plural base stations connected thereto. The radio network controllers are typically connected to one or more core networks.
One example of a radio access network is the Universal Mobile Telecommunications (UMTS) Terrestrial Radio Access Network (UTRAN). The UTRAN is a third generation system which in some respects builds upon the radio access technology known as Global System for Mobile communications (GSM) developed in Europe. UTRAN is essentially a wideband code division multiple access (W-CDMA) system.
As those skilled in the art appreciate, in W-CDMA technology a common frequency band allows simultaneous communication between a user equipment unit (UE) and plural base stations. Signals occupying the common frequency band are discriminated at the receiving station through spread spectrum CDMA waveform properties based on the use of a high speed, pseudo-noise (PN) code. These high speed PN codes are used to modulate signals transmitted from the base stations and the user equipment units (UEs). Transmitter stations using different PN codes (or a PN code offset in time) produce signals that can be separately demodulated at a receiving station. The high speed PN modulation also allows the receiving station to advantageously generate a received signal from a single transmitting station by combining several distinct propagation paths of the transmitted signal. In CDMA, therefore, a user equipment unit (UE) need not switch frequency when handoff of a connection is made from one cell to another. As a result, a destination cell can support a connection to a user equipment unit (UE) at the same time the origination cell continues to service the connection. Since the user equipment unit (UE) is always communicating through at least one cell during handover, there is no disruption to the call. Hence, the term “soft handover.” In contrast to hard handover, soft handover is a “make-before-break” switching operation.
The Universal Mobile Telecommunications (UMTS) Terrestrial Radio Access Network (UTRAN) accommodates both circuit switched and packet switched connections. In this regard, in UTRAN the circuit switched connections involve a radio network controller (RNC) communicating with a mobile switching center (MSC), which in turn is connected to a connection-oriented, external core network, which may be (for example) the Public Switched Telephone Network (PSTN) and/or the Integrated Services Digital Network (ISDN). On the other hand, in UTRAN the packet switched connections involve the radio network controller communicating with a Serving GPRS Support Node (SGSN) which in turn is connected through a backbone network and a Gateway GPRS support node (GGSN) to packet-switched networks (e.g., the Internet, X.25 external networks).
There are several interfaces of interest in the UTRAN. The interface between the radio network controllers (RNCs) and the core network(s) is termed the “Iu” interface. The interface between a radio network controller (RNC) and its base stations (BSs) is termed the “Iub” interface. The interface between the user equipment unit (UE) and the base stations is known as the “air interface” or the “radio interface” or “Uu interface”. An interface between radio network controllers (e.g., between a Serving RNC [SRNC] and a Drift RNC [DRNC]) is termed the “Iur” interface.
The radio network controller (RNC) controls the UTRAN. In fulfilling its control role, the RNC manages resources of the UTRAN. Such resources managed by the RNC include (among others) the downlink (DL) power transmitted by the base stations; the uplink (UL) interference perceived by the base stations; and the hardware situated at the base stations. Some of the hardware at the base stations can take the form of devices which are mounted on “boards” such as circuit boards.
Ideally an RNC attempts to manage UTRAN resources as efficiently as possible, thereby providing the greatest possible capacity (e.g., the largest number of possible connections between users) while maintaining an expected/desired quality for each connection. But in order to manage efficiently, the RNC must have fairly accurate and complete information about the services being carried by the UTRAN and the load in the portions of the network controlled by the RNC. This means that information about the load of a base station controlled by the RNC must be communicated to the RNC.
It would be impractical to communicate continuously the exact load situation in a given base station to its controlling RNC. To communicate the exact load situation, all status information for all hardware elements, e.g., boards, comprising the base station would have to be transmitted or transferred over the Iub interface to the RNC which manages the base station. Communication of such extensive load information would undersireably congest the Iub interface.
In recognition of the need to balance reporting of base station resource loading with efficient use of the Iub interface, a “Resource Status Indication” message has been proposed in Third Generation Partnership Project (3GPP) Specification 25.433 “UTRAN Iub Interface NBAP Signalling”. The Third Generation Partnership Project (3GPP) has undertaken to evolve further the UTRAN and GSM-based radio access network technologies. The “Resource Status Indication” message, described, e.g., in the Third Generation Partnership Project (3GPP) Specification 25.433§8.2.15 and §9.1.31, is sent from a base station node (e.g., “Node B”) to its controlling RNC upon occurrence of specific events, and contains some approximating information regarding usage of hardware resources. The information reported by the base station in the “Resource Status Indication” message is generally expressed in terms of so-called “Consumption Laws”. These laws indicate the amount of resources utilized for a connection given the spreading factor (SF) of the connection. The RNC then estimates the amount of resources being utilized at the base station by adding up the resource usage of each individual connection, taking this consumption law into account.
The proposed 3GPP “Resource Status Indication” message has deficiencies. Some of these deficiencies are rooted in the fact that the load on the base station node cannot always be expressed as a sum of the resource usage of each individual connection. As a first example deficiency, fragmentation problems at the base station node may render the sum misleading. Fragmentation can occur, for example, in a multi-board base station node in which spare capacity is scattered in an unusable fashion over several boards. In other words, while the sum contemplated by the 3GPP “Resource Status Indication” message may imply a certain spare capacity, not all the spare capacity is usable in view of the fragmentation.
To illustrate the problem of fragmentation, suppose that there are a number of the same boards in a base station and three classes of connections exist, particularly connection classes A, B, and C. Further suppose that each of the three boards can handle either of the following: (1) three class A connections; (2) two class B connections; (3) one class C connection or a class A connection and a class B connection. Thus, in terms of Consumption laws, A=1; B=1.5, and C=3. A correct load value for the base station can be found when all connections are the same class, but when the connections are of mixed classes, the sum does not hold. When several boards have mixed class allocations like this, more resources seem to be free than actually is the case.
A second example deficiency is that the sum reported by the 3GPP “Resource Status Indication” message may not be accurate when more than one resource type is used for a connection. Suppose, for sake of illustration, that there are two kinds of boards involved in a connection. A first kind of board (board type P) uses one circuit per connection regardless of the spreading factor (e.g., board type P can carry ten connections). The use of resources on a second type of board (board type Q), however, depends on the spreading factor of the connections on the board. Suppose that board type Q has twenty circuits. Suppose further that connection class A uses one circuit each, and connection class B uses four circuits each. Table 1 shows maximum combinations under either of two consumption laws (the first consumption law being A=2, B=2; the second consumption law being A=1, B=4). From Table 1 it can be seen that using the first consumption law will work when many of the class A connections are in the system, while the second consumption law will work when many class B connections are in the system.
TABLE 1FirstConsumptionLawA = 2, B = 2,Second Consumption LawMaximum Combinationslimit = 20A = 1, B = 4, limit = 2010xA + 0Xb 20109xA + 1Xb20138xA + 2Xb20167xA + 3Xb20194xA + 4Xb1620
What is needed, therefore, and an object of the present invention, is a technique for providing more accurate information regarding the load on a base station node in a radio access network.